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HomeMy WebLinkAboutCT 12-07; VALLEY 17 LOT 13; PRELIMINARY GEOTECHNICAL RECOMMENDATIONS; 2018-01-09ALTA CALIFORNIA GEOTECHNICAL INC. ANDRE LECOMPTE 1603 Frazier Avenue Carlsbad, California 92008 Attention: Subject: Mr. Andre Lecompte, Homeowner 170 North Maple Street, Suite 108 Corona, CA 92880 www.altageotechnical.com January 9, 2018 Project Number 2-0068 PRELIMINARY GEOTECHNICAL RECOMMENDATIONS Proposed Back and Side Yard Retaining Wall 1603 Frazier Avenue (AKA Lot 13 of the Valley 17 Project) JAN 11 2018 City of Carlsbad, California Lt f \y) ll t'J -tn . t)ul'° 4,f D ·tf.11 -Grt fDft .. oors-"'t..o r, on References: {_ ~ut tie" 2.) See Appendix A Mr. Andre Lecompte: Presented herein are Alta California Geotechnical, lnc.'s (Alta) preliminary geotechnical recommendations for the proposed back and side yard retaining wall for 1603 Frazier Avenue (AKA Lot 13 of the Valley 17 project, Tentative Tract CT 12-07), located at Valley Street and Oak Avenue, in the City of Carlsbad, County of San Diego, California. The conclusions and recommendations presented in this report are based on the plans provided by Ben Lund Engineering (redlines dated October 14, 2017, sheets 2 and 9 of 13), Alta's familiarity with the site (Alta, 2013; 2016) and review of the referenced reports. Alta's review of the data and site plan indicates that the construction of the proposed retaining wall is feasible, from a geotechnical standpoint, provided that the recommendations presented in this report are incorporated into the construction and backfill of the retaining wall. Included in this report are: • Discussion of the site geotechnical conditions; • Geotechnical recommendations for site construction; • Preliminary retaining foundation design parameters. San Diego Office Phone: 858.674.6636 Corona Office Phone: 951 .509.7090 T Project No. 2-0127 January 9, 2018 Page 2 Alta California Geotechnical, Inc. appreciates the opportunity to present this proposal. We will be happy to meet with you regarding the project at your convenience. Should you have any questions, please contact the undersigned at 619-920-2694. g. Exp.: 10-31-19 Certified Engineering Geologi Vice President President . . . ·1 .:,r-~~ !"41 : • .... Distribution: (1) Addressee ALTA CALIFORNIA GEOTECHNICAL, INC. Project No. 2-0127 January 9, 2018 1.0 PROJECT DESCRIPTION AND PROPOSED CONSTRUCTION Page 3 Lot 13 was graded under the observation and testing of Alta California Geotechnical, Inc. (2016) during October 2014 through June 2015. A minor second phase of grading was undertaken in February 2016 to finish the south-and west-facing 2:1 (horizontal:vertical) engineered fill slopes which descend into the water quality basin from the back and side yards of Lot 13. During grading, unsuitable soil removal operations were conducted to remove any undocumented artificial fill, top soil and highly weathered Old paralic deposits prior to the placement of engineered fill, such .. that all engineered fill is in direct contact with competent Old paralic deposits. Removal depths ranged from 3 to 4 feet below the existing ground surface. The depth of engineered fill beneath Lot 13 ranges from approximately 7.5 to 13.5 feet. The existing water quality basin located in the back and side yards of Lot 13 is bounded on the west and south sides by a retaining wall that is approximately five-(5) feet in height and on the east and north sides by 2:1 engineered fill slopes that is approximately 5-feet in height. As depicted on the 10-scale precise grading redline plans (Sheets 2 and 9 of 13) by Ben Lund Engineering, construction of an approximate 6.5-foot-high retaining wall retaining is proposed to be founded along the toe of the existing 2:1 engineered fill slopes. A level backfill behind the wall is proposed. Groundwater was not encountered during this firm's preliminary subsurface investigation (Alta, 2013) and during mass grading (Alta, 2016). The depth to groundwater table at the intersection of Carlsbad Village Drive and Interstate 5 has reported to be approximately 15 feet below the surface (Gregg Drilling and Testing, 2000), for a corresponding elevation of 73 feet above sea level. Considering this data and interpolating to the site Alta estimates the depth to groundwater table beneath the subject site is approximately 90 feet below the ground surface. However, it is possible ALTA CALIFORNIA GEOTECHNICAL, INC. Project No. 2-0127 January 9, 2018 Page 4 that perched groundwater exists or will exist in the water quality basin depending on precipitation and local irrigation practices. This report contains Alta California Geotechnical, lnc.'s (Alta's) findings, conclusions, and geotechnical recommendations for the construction of the subject retaining wall. 2.0 ENGINEERING PROPERTIES 2.1 Excavation Characteristics Based on Alta's review of the existing the data it is our opinion that the majority of the on-site materials possess favorable excavation characteristics. 2.2 Hydro-consolidation The underlying Old Paralic Deposits generally have a low potential for hydro- collapse. Based on the anticipated limited height fills and loading, and the accomplished removals during mass grading (Alta, 2016), the potential for hydro- collapse to occur at the site will be low and within foundation design tolerances upon the completion of recommendations presented herein. Design settlement recommendations are presented in Section 4.1. 2.3 Compressibility Compressible undocumented fills, topsoil and highly weathered Old Paralic Deposits were completely removed during grading, and as such, the wall footing can be founded in competent Old paralic deposits or engineered fill. 2.4 Expansion Potential Expansion index testing was performed on a sample taken from Lot 13 (Alta, 2016). The result indicate that the onsite soil is "very low" in expansion potential when tested per ASTM D: 4829. ALTA CALIFORNIA GEOTECHNICAL, INC. Project No. 2-0127 January 9, 2018 Page 5 2.5 Engineering Analysis Presented below is a general discussion of the engineering analysis methods that were utilized to develop the conclusions and recommendations presented in this report. 2.5.1 Bearing Capacity and Lateral Earth Pressures Ultimate bearing capacity values were obtained using the graphs and formula presented in NAVFAC DM-7.1. Allowable bearing was determined by applying a factor of safety of at least 3 to the ultimate bearing capacity. Static lateral earth pressures were calculated using Rankine methods for active and passive cases. If it is desired to use Coulomb forces, a separate analysis specific to the application can be conducted. 3.0 CONCLUSIONS AND RECOMMENDATIONS Based on Alta's findings during our observations and testing conducted during rough grading, the laboratory test results, our staff's previous experience in the area, and a review of the referenced reports, it is Alta's opinion that the development of the site is feasible from a geotechnical perspective. Presented below are recommendations that should be incorporated into site development and construction plans. Retaining wall footing excavations and backfill operations should be accomplished under the observation and testing of the project geotechnical consultant in accordance with the recommendations contained herein and the requirements of the City of Carlsbad. 3.1 Retaining Wall Footings Retaining wall footings should be entirely founded in competent Old paralic deposits or engineered fill. Cross section details on Sheet 2 of 13 indicate that the top of footing is to be located on foot below the horizontal section of the ALTA CALIFORNIA GEOTECHNICAL, INC. Project No. 2-0127 January 9, 2018 Page 6 impermeable PVC geomembrane liner, which rests directly on engineered fill or competent Old paralic deposit. Although unlikely, any undocumented fill or topsoil encountered during the footing excavations should be removed and recompacted such that the footing is entirely supported by engineered fill and/or competent Old paralic deposits. The representative Project Geotechnical Consultant should observe the footing excavations to verify this condition. 3.2 Retaining Wall Backfill All retaining wall backfill shall be compacted to a minimum relative compaction of 90 percent, as determined by ASTM Test Method: D-1557. Fill material should be moisture conditioned to optimum moisture or above, and as generally discussed in Alta's Earthwork Specification Section presented in Appendix B. Compaction shall be achieved with the use of sheepsfoot rollers or similar kneading type equipment. Mixing and moisture conditioning will be required in order to achieve the recommended moisture conditions. Fill should be placed in eight-inch bulk maximum lifts, moisture conditioned to optimum moisture content or above, compacted and tested as grading/construction progresses until final grades are attained. 3.3 Import Soils It is anticipated the backfill soils will necessarily be imported to the site. Import soils should consist of clean, low expansive, structural quality, compactable materials similar to the on-site soils and should be free of trash, debris or other objectionable materials. The project Geotechnical Consultant should be notified not less than 72 hours in advance of the locations of any soils proposed for import. Import sources should be sampled, tested, and approved by the project Geotechnical Consultant at the source prior to the importation ofthe soils to the site. The characteristics of the backfill soils should comply with the recommendations outlined below under Section 4.0 Design Considerations. The AL TA CALIFORNIA GEOTECHNICAL, INC. Project No. 2-0127 January 9, 2018 project Civil Engineer should include these requirements on plans and specifications for the project. 3.4 Backcut Stability Page 7 Temporary backcuts, if required during construction of the retaining wall, should be made no steeper than 1:1 without review and approval of the geotechnical consultant. Flatter backcuts may be necessary where geologic conditions dictate and where minimum width dimensions are to be maintained. Care should be taken during remedial grading operations in order to minimize risk of failure. Should failure occur, complete removal of the disturbed material will be required. In consideration of the inherent instability created by temporary construction backcuts for footing excavations, it is imperative that construction schedules are coordinated to minimize the unsupported exposure time of these excavations. Once started these excavations and subsequent retaining wall footing construction and backfill operations should be maintained to completion without intervening delays imposed by avoidable circumstances. In cases where five-day workweeks comprise a normal schedule, grading should be planned to avoid exposing at-grade or near-grade excavations through a non-work weekend. Where improvements may be affected by temporary instability, either on or offsite, further restrictions such as slot cutting, extending work days, implementing weekend schedules, and/or other requirements considered critical to serving specific circumstances may be imposed. 3.5 Basin Capacity Constructing the proposed retaining wall may alter the capacity of the subject WQMP basin. The project civil engineer should verify that the basin will function as intended with the proposed retaining wall. ALTA CALIFORNIA GEOTECHNICAL, INC. Project No. 2-0127 January 9, 2018 4.0 DESIGN CONSIDERATIONS Page 8 4.1 Retaining Wall Foundations Foundations may be designed based on the values presented in Table 4-1 below. Table 4-1 Foundation Design Parameters• Allowable Bearing 2000 lbs/ft2(assuming a minimum width and embedment of 12- inches). Lateral Bearing 250 lbs/ft' at a depth of 12 inches plus 250 lbs/ft' for each additional 12 inches of embedment to a maximum of 2000 lbs/ft' Sliding Coefficient 0.30 Differential Settlement Dynamic Differential= Y, inch in 40 feet Static Differential = % inch in 40 feet "'These values may be increased as allowed by Code to resist transient loads such as wind or seismic. Building code and structural design considerations may govern depth and reinforcement requirements and should be evaluated. 4.2 Seismic Design The site has been identified as "D" site class in accordance with CBC, 2016, Table 1613.5.3 (1). Utilizing this information, the computer program USGS Seismic Design Maps Version 3.1.0 and ASCE 7-10 criterion, the spectral response accelerations that can be utilized for the project are presented on Figure 1. These parameters should be verified by the structural engineer. Additional parameters should be determined by the structural engineer based on the Occupancy Category of the proposed structures. 4.3 Retaining Wall Design Retaining walls should be founded on compacted fill and/or competent Old Paralic deposits and should be backfilled with select granular soils that allow for drainage behind the wall. Foundations may be designed in accordance with the recommendations presented in Table 4-1, above. Unrestrained walls, free to rotate at least 0.001 radians, may be designed to resist lateral pressures imposed ALTA CALIFORNIA GEOTECHNICAL, INC. ~USGS Design Maps Summary Report User-Specified Input Report Title 2-0127 Tue January 9, 2018 00:48:33 UTC Building Code Reference Document ASCE 7-10 Standard (which utilizes USGS hazard data available in 2008) Site Coordinates 33.165°N, 117.335°W Site Soil Classification Site Class D -"Stiff Soil" Risk Category I/II/III USGS-Provided Output Ss = 1.128 g S1 = 0.433 g S,,s = 1.183 g S,,1 = 0.679 g Sos= 0.789 g So, = 0.453 g For information on how the SS and 51 values above have been calculated from probabilistic (risk-targeted) and deterministic ground motions in the direction of maximum horlzontal response, please return to the application and select the "2009 NEHRP" building code reference document. ·;:o "" <:Yi ) ·; ~;{ ,::; ·'Y1 l",· H,.tJ +--1----+--+--+----lf---+--+--+---+-~ p.,,,,0:1. r <•~) For PGA.,, T,, c .. , and Cu values, please yiew the detailed report. •1.W an o.,;) +--l---+--+--+----<---+---+--+---1---1 GOO u~ a0 am ~ID ,m l» 1m LOO ,~ :w P~r,,c,d. r (11~·) FIGURE 1 Project No. 2-0127 January 9, 2018 Page 9 by a fluid with a unit weight determined in accordance with the Table 4-2 below. The table also presents design parameters for restrained (at-rest) retaining walls. These parameters may be used to design retaining walls that may be considered as restrained due to the method of construction or location (corner sections of un restrained retaining walls). TABLE 4-2 Equivalent Fluid Pressures for Select 90% Compacted Fill Backfill I Active jpsf/ft) I At-Rest (psf/ft) Level I 35 I 55 Per the requirements of the 2016 CBC, the seismic force acting on the retaining walls with backfill exceeding 6-feet in height may be resolved utilizing the formula 13H2 lb/lineal ft (H=height of the wall). This force acts at approximately 0.6H above the base of the wall. The seismic value can be converted as required by the retaining wall. engineer. Retaining walls should be designed in general accordance with Section 1807 A.2 of the 2016 CBC. ;,,, Restrained retaining walls should be designed for "at-rest" conditions. ~ The design loads presented in the above table are to be app lied on the retaining wall in a horizontal fashion and as such friction between wall and retained soils should not be allowed in the retaining wall analyses. ~ Additional allowances should be made in the retaining wall design to account for the influence of construction loads, temporary loads, and possible nearby structural footing loads. ~ S~lect backfill should be granular, structural quality backfill with a Sand ~~uivalent of 20 or better and an ASCE Expansion Index of 20 or less. The backfill must encompass the full active wedge area. The upper one foot of backfill should be comprised of native on-site soils (see Plate A). ~The wall design should include waterproofing (where appropriate) and C/ backdrains or weep holes for relieving possible hydrostatic pressures. The backdrain should be comprised of a 4-inch perforated PVC pipe in a 1 ft. by 1 ft., %-inch gravel matrix, wrapped with a geofabric. The backdrain should ALTA CALIFORNIA GEOTECHNICAL, INC. Project No. 2-0127 January 9, 2018 Page 10 be installed with a minimum gradient of 2 percent and should be outletted to an appropriate location. For subterranean walls this may include drainage by sump pumps. >" No backfill should be placed against concrete until minimum design strengths are achieved in compression tests of cylinders. It should be noted that the bearing values presented in Table 4-1 are based on level conditions at the toe. Modified design parameters can be presented for retaining walls with descending slope conditions at the toe. Other conditions should be evaluated on a case by case basis. 4.4 Footing Excavations The excavations should be cleaned of all loose/sloughed materials and be neatly trimmed at the time of concrete placement. Footing excavations should be observed by the Project Geotechnical Consultant prior to the placement of concrete to determine that the excavations are founded in suitable material. 4.5 Concrete Design Negligible concentrations of sulfates were detected in the onsite soils for Lot 13 (Alta, 2013). Therefore, the use of sulfate resistant concrete is not required per ACI 318-14. 4.6 Corrosion The onsite soils may be mildly corrosive to buried metal objects (Romanoff, 1989) based on testing for Lot 13 by Alta (2013). Consideration should be given to protecting buried metals from corrosion. Typical measures include using non- corrosive backfill, protective coatings, wrapping, or a combination of these methods in accordance with the manufacturer's recommendations. A corrosion engineer should be consulted if specific recommendations are required. Post- ALTA CALIFORNIA GEOTECHNICAL, INC. Project No. 2-0127 January 9, 2018 Page 11 grading conditions should be evaluated and final recommendations concerning corrosion should be made at that time. 4.7 Site Drainage Positive drainage away from the exisiting residential structure should be provided and maintained. Roof, pad and lot drainage should be collected and directed away from the structures toward approved disposal areas through drainage terraces, gutters, down drains, and other devices. Design fine grade elevations should be maintained through the life of the structure or if design fine grade elevations are altered, adequate area drains should be installed in order to provide rapid discharge of water, away from structures. Residents or Homeowner Associations should be made aware that they are responsible for maintenance and cleaning of all drainage terraces, down drains, and other devices that have been installed to promote site and structure drainage. 5.0 FUTURE PLAN REVIEWS This report represents a geotechnical review of the 10-scale plan provided by Ben Lund Engineering and dated October 14, 2017. As the project design progresses, site specific geologic and geotechnical issues should be considered in the design and construction of the project. Consequently, future plan reviews may be necessary. These reviews may include reviews of: ;;, Foundation Plans These plans should be forwarded to the project Geotechnical Consultant for review. 6.0 CLOSURE For the purposes of this report, multiple working hypotheses were established for the project, utilizing the available data and the most probable model is used for the analysis. Future information collected during the proposed construction operation is intended to evaluate the hypothesis and as such, some of the assumptions ALTA CALIFORNIA GEOTECHNICAL, INC. Project No. 2-0127 January 9, 2018 Page 12 summarized in this report may need to be changed. Some modifications of the grading recommendations may become necessary, should the conditions encountered in the field differ from the conditions hypothesized in this report. Plans and sections of the project specifications should be reviewed by Alta, to evaluate conformance with the intent of the recommendations contained in this report. If the project description or final design varies from that described in herein, Alta must be consulted regarding the applicability of the recommendations contained herein and whether any changes are required. Alta accepts no liability for any use of its recommendations if the project description or final design varies and Alta is not consulted regarding the alterations. This report is based on the following: 1) the project as presented on the attached plan; 2) the information obtained from the; 2) as-graded laboratory test results (Alta, 2016); and 3) from the information presented in the referenced reports. The findings and recommendations are based on the results of the subsurface investigation, laboratory testing, observation and testing conducted during grading (Alta, 2016) and office analysis combined with an interpolation and extrapolation of conditions between and beyond the observation and testing locations. However, the materials adjacent to or beneath those observed may have different characteristics than those observed and no precise representations are made as to the quality or extent of the materials not observed. The findings are also based on information from previous investigations/geotechnical reports contained in the references. The results reflect an interpretation of the direct evidence obtained. Work performed by Alta has been conducted in a manner consistent with the level of care and skill ordinarily exercised by members of the geotechnical profession currently practicing in the same locality under similar conditions. No other representation, either expressed or implied, and no warranty or guarantee is included or intended. ALT A CALIFORNIA GEOTECHNICAL, INC. Project No. 2-0127 January 9, 2018 Page 13 The recommendations presented in this report are based on the assumption that an appropriate level of field review during construction will be provided by a geotechnical consultant who is familiar with the design and site geologic conditions. That field review shall be sufficient to confirm that geotechnical and geologic conditions exposed during construction are consistent with the geologic representations and corresponding recommendations presented in this report. The conclusions and recommendations included in this report are applicable to the specific design of this project as discussed in this report. They have no applicability to any other project or to any other location and any and all subsequent users accept any and all liability resulting from any use or reuse of the data, opinions, and recommendations without the prior written consent of Alta. Alta has no responsibility for construction means, methods, techniques, sequences, procedures, safety precautions, programs in connection with the construction, acts or omissions of the CONTRACTOR or any other person performing any of the construction, or for the failure of any of them to carry out the construction in accordance with the final design drawings and specifications. ALTA CALIFORNIA GEOTECHNICAL, INC, APPENDIX A REFERENCES ALTA CALIFORNIA GEOTECHNICAL, INC. Project Number 2-0127 January 9, 2018 APPENDIX A Selected References Page A-1 Alta California Geotechnical, Inc., 2016, Precise grading report, Lots 13 and 17 of Tract CT 12-07, The Valley 17 project, City of Carlsbad, California dated February 11, 2016 (Project No. 2- 0068). Alta California Geotechnical, Inc., 2013, Preliminary geotechnical investigation, Tentative Tract CT 12-07, Valley Street and Oak Avenue, City of Carlsbad, California dated October 24, 2013 (Project No. 2-0127). Ben Lund Engineering, 2017, Redlines on Precise grading plans by Huitt-Zollars, Inc. (Sheet 2 and 9 of 13). California Division of Mines and Geology, 2008, Guidelines for evaluating and mitigating seismic hazards in California: Department of Conservation, Special Publication 117a. CalTrans, 2003, Corrosion Guidelines, California Department of Transportation Division of Engineering Services Materials Engineering and Testing Services Corrosion Technology Branch, Version 1.0, September 2003. Gregg Drilling and Testing, Inc., 2000, Groundwater Depth Table, Southern California, Carlsbad, March 8, 2000. Hart, E. W., 1994, Fault-rupture hazard zones in California: California Division of Mines and Geology, special publication 42, 1992 revised edition, 34 p. Jennings, C. W., 1994, Fault activity map of California and adjacent areas: California Division of Mines and Geology, California geologic map data series, map no. 6, scale 1:750,000. Jennings, C. W., 1985, An explanatory text to accompany the 1:750,000 scale fault and geologic map of California: California Division of Mines and Geology, special publication 42, revised 1985, 24 p. Kennedy, M.P. and Tan, S.S., 2005, Geologic Map of the Oceanside 30' x 60' Quadrangle, California: California Geologic Survey, Regional Geologic Map Series, 1:100,000 Scale, Map No. 3 Sheet 1 and 2 of 2. Stantec, Phase II Environmental Site Assessment, Vacant Lot, Southwest Corner of Valley Street and Oak Avenue, Carlsbad, California, 92008, March 30, 2012. Stantec, Phase I Environmental Assessment, Vacant Lot Southwest Corner of Valley Street and Oak Avenue, Carlsbad, California, 92008, January 31, 2012. ALTA CALIFORNIA GEOTECHNICAL, INC. Project No. 2-0127 January 9, 2018 Page A-2 Tan, S.S. and Kennedy, M.P., 1996, Geologic Maps of the Northwestern Part of San Diego County, California: California Geologic Survey, Regional Geologic Map Series, Platel. Tan, S.S. and Giffen, G.G., 1995, landslide Hazards in the Northern Part of the San Diego Metropolitan area, San Diego County, California: California Division of Mines and Geology Open File-Report 95-04. Weber, F.H., 1982, Recent Slope Failures, Ancient landslides, and Related Geology of the North- Central Coastal Area, San Diego County, California: California Division of Mines and Geology Open-File Report 82-12 LA. AL TA CALIFORNIA GEOTECHNICAL, INC. APPENDIX B Earthwork Specifications AL TA CALIFORNIA GEOTECHNICAL, INC. ALTA CALIFORNIA GEOTECHNICAL, INC. EARTHWORK SPECIFICATIONS These specifications present the generally accepted standards and minimum earthwork requirements for the development of the project. These specifications shall be the project guidelines for earthwork except where specifically superseded in preliminary geology and soils reports, grading plan review reports or by the prevailing grading codes or ordinances of the controlling agency. A. GENERAL 1. The Contractor shall be responsible for the satisfactory completion of all earthwork in accordance with the project plans and specifications. 2. The project Geotechnical Engineer and Engineering Geologist, or their representatives, shall provide observation and testing. services, and Geotechnical consultation for the duration of the project. 3. All clearing, grubbing, stripping and site preparation for the project shall be accomplished by the Contractor to the satisfaction of the Geotechnical Engineer/Engineering Geologist. 4. It is the Contractor's responsibility to prepare the ground surface to receive fill to the satisfaction of the Geotechnical Engineer and to place, spread, mix, moisture condition, and compact the fill in accordance with the job specifications and as required by the Geotechnical Engineer. The Contractor shall also remove all material considered by the Geotechnical Engineer to be unsuitable for use in the construction of engineered fills. 5. The Contractor shall have suitable and sufficient equipment In operation to handle the amount of fill being placed. When necessary, equipment will be shut down temporarily in order to permit the proper preparation of fills. B. PREPARATION OF FILL AREAS 1. Excessive vegetation and all deleterious material should be disposed of offslte as required by the Geotechnical Engineer. Existing fill, soil, alluvium or rock materials determined by the Geotechnical Engineer as being unsuitable for placement in compacted fills shall be removed and hauled from the site. Where applicable, the Contractor may obtain the ALTA CALIFORNIA GEOTECHNICAL1 INC. Earthwork Specifications Page 2 approval of the Soils Engineer and the controlling authorities for the project to dispose of the above described materials, or a portion thereof, in designated areas onsite. After removal of the deleterious materials have been accomplished, earth materials deemed unsuitable in their natural, in-place condition, shall be removed as recommended by the Geotechnical Engineer/Engineering Geologist. 2. Upon achieving a suitable bottom for fill placement, the exposed removal bottom shall be disced or bladed by the Contractor to the satisfaction of the Geotechnical Engineer. The prepared ground surfaces shall then be brought to the specified moisture content mixed as required, and compacted and tested as specified. In localities where it is necessary to obtain the approval of the controlling agency prior to placing fill, it will be the Contractor's responsibility to contact the proper authorities to visit the site. 3. Any underground structure such as cesspools, cisterns, mining shafts, tunnels, septic tanks, wells, pipelines or other structures not located prior to grading are to be removed or treated in a manner prescribed by the Geotechnical Engineer and/or the controlling agency for the project. C. ENGINEERED FILLS l. Any material imported or excavated on the property may be utilized as fill, provided the material has been determined to be suitable by the Geotechnical Engineer. Deleterious materials shall be removed from the fill as directed by the Geotechnical Engineer. 2. Rock or rock fragments less than twelve Inches In the largest dimension may be utilized in the fill, provided they are not placed in concentrated pockets and the distribution of the rocks is approved by the Geotechnical Engineer. 3. Rocks greater than twelve inches in the largest dimension shall be taken offsite, or placed in accordance with the recommendations of the Geotechnlcal Engineer In areas designated as suitable for rock disposal, 4. All materials to be used as fill, shall be tested in the laboratory by the Geotechnical Engineer. Proposed import materials shall be approved by the Geotechnical Engineer 48 hours prior to importation. 5. The fill materials shall be placed by the Contractor in lifts, that when compacted, shall not exceed six inches. Each lift shall be spread evenly and shall be Al.TA CALIFORNIA GEOTECHNICAL, INC, Earthwork Specifications Page 3 thoroughly mixed to achieve a near uniform moisture condition and a uniform blend of materials. All compaction shall be achieved at or above the optimum moisture content, as determined by the applicable laboratory standard. The Contractor will be notified if the fill materials are too wet or too dry to achieve the required compaction standard. 6. When the moisture content of the fill material is below the limit specified by the Geotechnlcal Engineer, water shall be added and the materials shall be blended until a uniform moisture content, within specified limits, is achieved. When the moisture content of the fill material is above the limits specified by the Geotechnical Engineer, the fill materials shall be aerated by discing, blading, mixed with dryer fill materials, or other satisfactory methods until the moisture content is within the specified limits. 7. Each fill lift shall be compacted to the minimum project standards, in compliance with the testing methods specified.by the controlling governmental agency, and in accordance with recommendations of the Geotechnlcal Engineer. In the absence of specific recommendations by the Geotechnical Engineer to the contrary, the compaction standard shall be the most recent version of ASTM:D 1557. 8. Where a slope receiving fill exceeds a ratio of five-horizontal to one-vertical, the fill shall be keyed and benched through all unsuitable materials into sound bedrock or firm material, in accordance with the recommendations and approval of the Geotechnical Engineer. 9. Side hlll fills shall have a minimum key width of 15 feet into bedrock or firm materials, unless otherwise specified In the soil report and approved by the Geotechnlcal Engineer in the field. 10. Drainage terraces and subdrainage devices shall be constructed In compliance with the ordinances of the controlling governmental agency and/or with the recommendations of the Geotechnical Engineer and Engineering Geologist. 11. The Contractor shall be required to maintain the specified minimum relative compaction out to the finish slope face of fill slopes, buttresses, and stabilization fills as directed by the Geotechnical Engineer and/or the governing agency for the project. This may be achieved by either overbuilding the slope and cutting ALTA CALIFORNIA GEOTECHNICAL, INC. Earthwork Specifications Page4 back to the compacted core; by direct compaction of the slope face with suitable equipment; or by any other procedure which produces the required result. 12. The fill portion of fill-over-cut slopes shall be properly keyed into rock or firm material; and the fill area shall be stripped of all soil or unsuitable materials prior to placing fill. The design cut portion of the slope should be made first and evaluated for suitability by the Engineering Geologist prior to placement of fill in the keyway above the cut slope. 13. Pad areas in cut or natural ground shall be approved by the Geotechnical Engineer. Finished surfaces of these pads may require scarification and recompaction, or over excavation as determined by the Geotechnical Engineer. D. CUTSLOPES 1. The Engineering Geologist shall observe all cut slopes and shall be notified by the Contractor when cut slopes are to be started. .. 2. If, during the course of grading, unforeseen adverse or potentially adverse geologic conditions are encountered, the Engineering Geologist and Soil Engineer shall investigate, analyze and make recommendations to remediate these problems. 3. Non-erodible interceptor swales shall be placed at the top of cut slopes that face the same direction as the superjacent, prevailing drainage. 4. Unless otherwise specified in specific geotechnlcal reports, no cut slopes shall be excavated higher or steeper than that allowed by the ordinances of controlling governmental agencies. 5. Drainage terraces shall be constructed in compliance with the ordinances of the controlling governmental agencies, and/or In accordance with the recommendations of the Geotechnical Engineer or Engineering Geologist. E. GRADING CONTROL 1. Fill placement shall be observed and tested by the Geotechnlcal Engineer and/or his representative during grading. Field density tests shall be made by the Geotechnlcal Engineer and/or his representative to evaluate the compaction and moisture compliance of each fill lift. Density tests shall be conducted at Intervals not to exceed two feet of fill ALTA CALIFORNIA GEOTECHNICAL, INC. Earthwork Specifications Page 5 height. Where sheepsfoot rollers are used, the fill may be disturbed to a depth of several inches. Density determinations shall be taken In the compacted material below the disturbed surface at a depth determined by the Geotechnical Engineer or his representative. 2. Where tests indicate that the density of any layer of fill, or portion thereof, is below the required relative compaction, or improper moisture content is in evidence, that particular layer or portion thereof shall be reworked until the required density and/or moisture content has been attained. Additional fills shall not be placed over an area until the previous lift of fill has been tested and found to meet the density and moisture requirements for the project and the previous lift is approved by the Geotechnical Engineer. 3. When grading activities are Interrupted by heavy rains, fill operations shall not be resumed until field observations and tests by the Geotechnlcal Engineer indicate the moisture content and density of the fill are within the specified limits. 4. During construction, the Contractor shall properly grade all surfaces to maintain good drainage and prevent the ponding of water. The Contractor shall take remedial action to control surface water and to prevent erosion of graded areas until such time as a permanent drainage and erosion devices have been installed. 5. Observation and testing by the Geotechnlcal Engineer and/or his representative shall be conducted during filling and compacting operations In order that he will be able to state in his opinion that all cut and filled areas are graded in accordance with the approved specifications. 6. Upon the completion of grading activities and after the Geotechnical Engineer and Engineering Geologist have finished their observations of the work, final reports shall be submitted. No further excavation or fill placement shall be undertaken without prior notification of the Geotechnical Engineer and/or Engineering Geologist. F. FINISHED SLOPES All finished cut and fill slopes shall be planted and irrigated and/or protected from erosion In accordance with the project specifications, governing agencies, and/or as recommended by a landscape architect. ALTA CALIFORNIA GEOTECHNICAL, INC.